1. Field of the Invention
This invention relates generally to instruments for determining jaw defects in animals, and more particularly to a gauge system for measuring underbite (brachygnathia superior) and overbite (brachygnatia inferior) in ruminants.
2. Background Art
All species of ruminants lack top incisors. All these animals have a tough dental pad below their top lip, sometimes referred to as the maxillary pad, instead of front teeth, and a huge gap between the dental pad (maxillary pad) and the back teeth Underbite (brachygnathia superior) and overbite (brachygnatia inferior) in ruminants are well know genetic jaw defects that develop as a result of several factors, including osteogenetic disorder, mechanical factors and heredity, and is characterized by failure of the premaxillary bone to grow to normal length and width.
A normal bite is known as the condition, when the mouth is closed in a bite position and the upper and lower jaw are perfectly aligned, the upper edge of the teeth crown (the part of a tooth external to the gum) is touching the front edge of the dental pad (maxillary pad) of the upper jaw.
Underbite (brachygnathia superior), also known as mandibular prognathism, although the first term is considered most correct, is a condition caused by failure of the premaxillary bone to grow to normal length and width. Prognathism refers to a protruding jaw. It is also called an extended chin. In this condition, when the mouth is closed in a bite position, the upper edge of the teeth crown is disposed forward of the front edge of the dental pad (maxillary pad) of the upper jaw.
Overbite (brachygnathia inferior), also known as mandibular brachygnathia, and commonly called parrot mouth prognathism, is a condition caused by failure of the anterior of the lower jaw forward of the premolars to grow to normal length, causing an abnormal shortness of the lower jaw. In this condition, when the mouth is closed in a bite position, the upper edge of the teeth crown is disposed rearward of the front edge, or anterior angle, of the dental pad (maxillary pad) of the upper jaw.
These jaw defects can lead to serious economic loses in bovine and sheep production systems, because it can seriously affect the grazing animal's ability to bite off foliage and have adequate nutrition.
Therefore it is important to be able identify and quantitatively measure these specific jaw defects in animals in order to select and eliminate those that have this problem, and also to have the ability to quantify the prevalence of underbite (brachygnathia superior) and overbite (brachygnatia inferior) in the animal population.
There are several patents directed toward gauge instruments for measuring various dental conditions. The following are several examples.
Rhein, U.S. Pat. No. 1,327,114, discloses an attachable or permanent depth gauge which is used with dental and medical instruments to for example, measure the length of a root canal. The gauge disclosed has two members, the first member being affixed or attached to the handle of the instrument and the second member being movable with respect to the first. Depth is measured by viewing an indicator which reflects the distance between the second member and the extremity of the instrument. The sliding gauge must be positioned to the zero point before the measurement is taken and the instrument must be removed from the patient's mouth in order to read the scale. Mayer et al. U.S. Pat. No. 4,997,368, discloses an oral measuring insert device having biased top and bottom surfaces which can be directed into the mouth between the frontal upper and lower teeth to measure the opening of the mouth. The device is formed from a lightweight, disposable plastic having arcuate grooves positioned within the upper and lower surfaces providing detents for the teeth. Numerical indicia is disposed along the side of the insert to allow the examiner to quickly determine the degree of movement the mandible has undergone at maximum insertion. Various sizes of the insert may be manufactured and made available for different mouth sizes such as for example with young children, older children or adults.
Sheridan, U.S. Pat. No. 5,044,951, discloses a dental space and periodontal cavity measuring instrument for insertion in interdental or interproximal spaces between teeth and in periodontal cavities in both the upper and lower dental arches to determine the width of such spaces and the depth of the cavities, respectively, for appropriate treatment. The dental space and periodontal cavity measuring instrument has a centrally located handle provided with a pair of oppositely-extending single tips or multiple, elongated, graduated cylinders which terminate in graduated ends, for insertion in the interdental spaces and periodontal cavities. The calibrated cylinders and graduated ends may be extended in a straight line from the handle, or one or more cylinders in one or both of the calibrated and graduated tips may be angulated and the diameter of each cylinder may be indicated on the handle for size-identification purposes. The ends of the cylinder or stem tips may also be “waffled” with striations for ligature tucking purposes.
Urban, U.S. Pat. No. 5,676,544, discloses an instrument for subgingival scaling, root planing and maintenance of periodontal health. The instrument has an elongated body with a handle portion, a terminal shank portion, a working end, and a gauge. The terminal shank portion includes a base having a first portion, which is coaxial with the handle portion, and a second portion, which is angled from the first portion. The working end has a rear heel portion adjacent to the second portion and a front toe portion. Between the heel and toe there is a blade edge extending lengthwise. The gauge is arranged along the annular surface of the second portion of the terminal shank. In order to measure the periodontal health of the patient on whom the instrument is being used, the instrument is inserted into the periodontal space between the tooth and the gum. The depth of the periodontal space is determined by reading the marking on the gauge which meets the gumline.